Anti-filming system will fail

BBC News recently carried a story on an anti-filming system in development at the Georgia Institute of Technology. I predict it will fail miserably.


The technique relies on a little-known property of the CCD chips that power digital photography and video capture: retroreflectivity. The chips reflect light back to the source, so they can be detected by active scanning. Once a CCD is detected, the system shines a laser or bright narrow-beam light at the chip, flooding the sensor and preventing decent image capture.


The main application is piracy prevention at cineplexes, but the implications go much farther. (The article mentions possible usage at government facilities and trade shows, aimed at protecting national security and trade secrets.) This is a targeting of an entire technology, not a specific use of that technology. Who might want to detect hidden cameras? Think of all the uses of clandestine filming: activism, infiltration, exposés. Cameras represent openness and honesty, bringing the light of inquiry behind closed doors. Widespread use of camera-blinding would inevitably lead to a technical restriction on the right to film in public places.


I foresee several problems with this system.

  • Legitimate uses. CCDs are employed in assistive devices as well as in the establishment's own security cameras, neither of which should be blinded.
  • Damage to cameras (and eyes). The blinding is apparantly a temporary effect, but if it should prove to damage cameras, the establishments using the technology could be liable for thousands of dollars worth of equipment damage. (If the system misfires and shines light into people's eyes, there could also be medical consequences.)
  • False positives. As noted in the article,
    The biggest problem is making sure we don't get false positives from, say, a large shiny earring. We need to make our system work well enough so that it can find a dot, then test to see if it's reflective, then see if it's retroreflective, and then test to see if it's the right shape.


In the world of digital piracy, countermeasures need not be simple, easy, or inexpensive. Remember, all it takes is one pirate per movie. I present here several passive and active countermeasures:

  • Non-reflective lens covers. Creating a home-built one-way lens cover out of window tint sheets shouldn't be too difficult.
  • Lens filters. If the anti-filming system uses a specific frequency of light to either test for or blind CCDs, visible-light-only lens filters would likely block the system out.
  • Active counter-attack. The anti-piracy system itself uses digital cameras to detect and track CCDs. The system could be blinded by a rogue user using a portable version.
  • Flak. Scattering bits of retroflective glitter about the room might sufficiently confuse cameras.


Though this technique could potentially have a moderate negative impact on undercover investigations and photographers' rights, anyone with a little extra spending money should have no problem defeating the system. Unfortunately, countermeasure technology will likely not be as available as cheap digital cameras. I suspect that this technology will not assist anti-piracy efforts as much as the industry expects, and the cost to digital filming culture minor but not significant. Assessment: annoyance.

Responses: 2 so far

  1. Stanley says:

    Wow, good post. Where does this DRM craziness end? Sheesh.

  2. Tim McCormack says:

    I see this DRM nonsense as the flailings of a desperate industry. (They aren't necessarily sinking, but they sure think they are.)